In recent years, portable terminals having a foldable cover have become popular.
FIG. 1 is a perspective view showing a conventional foldable mechanism for opening and closing a portable terminal 400. FIG. 2 is an exploded perspective view a portion of the folding mechanism shown in FIG. 1.
This folding mechanism for a portable terminal includes a holder portion 412 fixed to a cover 410, a housing 300 inserted into and fixed to the holder portion 412, a first slip portion 320 rotatably housed inside of the housing 300, a second slip portion 330 fixedly housed inside of the housing and contacting the first slip portion 320, a spring 340 urging the second slip portion 330 towards the first slip portion 320, a first support portion 402 formed in a main body so as to engage the first slip portion 320, and a second support portion 406 formed in the main body so as to rotatably support the holder portion 412.
The holder portion 412 is provided at one side thereof with an opening 414 into which the housing 300 is inserted, and at the other side thereof with a rotation shaft 416 protruding so as to be rotatably coupled with the second support portion 406.
In addition, the housing 300 (FIG. 2) has an internal space 302 opened such that the first slip portion 320, the second slip portion 330 and the spring 340 are housed inside thereof. Formed in one side of the internal space 302 is a through hole 304 and in the other side of the internal space 302 is a protrusion 306.
The first slip portion 320 has a coupling shaft 322 passing through the through-hole 304, and a connection shaft 324 formed in the opposite side to the coupling shaft 322. Formed around the connection shaft 324 is a first cylinder portion 326, on top of which a first waveform face 328 is formed. The first waveform face 328 has a wave of two periods per rotation around the connection shaft 324.
The second slip portion 330 is provided with a connection hole 332 formed with which the connection shaft 324 is rotatably engaged. A second cylinder portion 334 is formed around the connection hole 332. Formed on top of the second cylinder portion 334 is a second waveform face 336 corresponding to the first waveform face 328.
The connection shaft 324 is inserted into the connection hole 332 so as to prevent the first and second slip portions 320 and 330 from being disengaged from each other, i.e., to allow a linear movement against each other when the first and second waveform faces 328 and 336 contact and rotate.
Further, the second slip portion 330 is formed with a sliding protrusion 338 at the lateral side. In the internal opening 302 of the housing 300, a sliding groove 308 is formed along the moving direction of the second slip portion 330 for the sliding protrusion 338 to be inserted into the sliding groove 308. Thus, the second slip portion 330 is allowed to carry out a linear movement, not a rotational motion.
On the other hand, one end of the spring 340 is coupled with the protrusion 306 and the other end thereof is housed in the internal space 302 so as to urge the second slip portion 330. The connection shaft 324 passes through the connection hole 332 and then is inserted into the spring 340 center to prevent the spring 340 from bending.
The first support portion 402 is formed with a fixing hole 404 to which the connection shaft 322 is fixed. The second support portion 406 is formed with a rotation hole 408 to which the rotation shaft 416 is rotatably coupled.
In the above conventional mechanism, however a single sliding groove 308 is provided in the housing 300 and a single sliding protrusion 338 is provided in the second slip portion 330. Thus, the connection between the housing 300 and the second slip portion 330 is unstable for this conventional foldable mechanism.
The first slip portion 320 is relatively stable since its coupling shaft 322 is coupled to the cover 410 to perform a rotational movement only. However, the second slip portion 330 may cause distortion during its linear movement along the connection shaft 324. Due to this distortion, the second slip portion 330 incurs frictional wear with the housing 300 and produces frictional noises. In addition, this frictional wear leads to shortening of the service life of the second slip portion 330.